Hydraulic picker stick check



Nov M 1950 e. H. HUFFERD 2,529,696

HYDRAULIC PICKER STICK CHECK Filed Sept. 24, 1948 2 Sheets-Sheet l Novo M 1950 e. H. HUFFERD 2,529,696

HYDRAULIC PICKER STICK CHECK Filed Sept. 24, 1948 2 Sheets-Sheet 2 g: 119 km; I245 if k 4 *5 In we m 227:

Patented Nov. 14, 1950 UNITED STATES PATENT OFFICE HYDRAULIC PICKER STICK CHECK George H. Hufierd, Cleveland, Ohio, assignor to Houdaille-Hershey Corporation, Detroit, Mich., a corporation of Michigan Application September 24, 1948, Serial No. 50,950

- 14 Claims. (c1.139 161' This invention relates to an hydraulic check unit, and particularly to an improved hydraulic check unit adaptable for use in checkin the movements of a picker stick of a loom.

As is well known, a loom picker stick continuously undergoes a cycle of movements involving very high rates of acceleration and deceleration at a cyclic rate approaching 180 or more cycles per minute. A picker stick is generally mounted on each end of the lay of the loom and its path of movement is controlled by well known linkages so that while the picker stick describes a generally pivoting movement, the top end thereof moves in a substantially straight line path. On its inward stroke, the picker stick accelerates and throws the shuttle at a very high velocity through the warp shed to the other side of the loom where a similar picker stick catches the shuttle and decelerates the shuttle, preliminary to throwin the shuttle back across the loom. Since the rate of production of any loom is determined primarily by the cyclic rate of the shuttle movements, there has been a continuous effort to increase the rate of shuttle cycles so that present day looms operate at 180 or more picks per minute. Obviously, the acceleration and deceleration forces exerted by and upon the picker stick when operatin at such high cyclic rate, are of tremendous magnitudes, hence it is of extreme importance that the movement of the picker stick be smoothly decelerated on either its inward or outward stroke in such a manner as to prevent the development of excessive forces therein. At the same time, the picker stick must be accurately positioned with respect to the shuttle box before the shuttle returns, so that in each cycle, the shuttle engages the picker stick at the substantially identical position and the picker stick stops the shuttle each time at the same position in the shuttle box.

If the forward or inward movement of the picker stick is not properly controlled, then, when the shuttle is expelled from the shuttle box, the shuttle is likely to be thrown wild and thus produce defective cloth. Of course, due to the high cyclic rate of operation, it is also very essential to yieldingly bring the picker stick to rest as soon as possible after its shuttle throwing stroke has been delivered. The checking of the movement of the picker stick on its outward stroke is equally important, because the impact of the incoming shuttle must be smoothly absorbed in such manner that the shuttle will not rebound but will be brought to rest at a predetermined position in the shuttle box. Again,

2 such checking action must be accomplished wit e in a comparatively, short travel of the picker stick.

It has heretofore been proposed to employ an hydraulic checkin device for effecting the necessary checking actions required for proper operation of the picker stick. However, since any such checking device must necessarily be of the double acting type and furthermore, since all looms vary slightly in their operating characteristics so that adjustment of the checking action exerted by the hydraulic checking device in either direction of the picker stick movement is required to be made upon not only the initial assemblage of the checking device to the loom but at frequent intervals thereafter, due to variations in the loom operatin characteristics produced by temperature, humidity, or wear of components, it is read:- ily apparent that conventionally constructed, double acting hydraulic check units are not ordinarily suitable for such application.

Accordingly, it is an object of this invention to provide an improved hydraulic check unit for checkin the movements of a picker stick of a loom, and particularly a double acting hydraulic check of the rotary type which may be directly incorporated in the control linkage of the picker stick.

Another object of this invention is to provide an improved double acting, rotary type hydraulic check unit of unusually compact construction which may be'supported in its entirety upon the pivotal connection of any two link member of the control linkage of the picker stick of the loom.

Still another object of this invention is to provide an improved rotary type, fluid checking device for checking the movements of the picker stick of the loom which is susceptible to rapid and convenient adjustment of its checking action.

A particular object of this invention is to provide an improved check unit for use in the control linkage of a picker stick of a loom, characterized by the provision of a bypass arrangement in the hydraulic chamber of the checkin unit plus a check valve disposed in such bypass so as to permit unimpeded return movement of the piston of the check unit from one of its extreme positions, such direction of return movement of the piston corresponding to the shuttle throwing or power stroke of the picker stick. g.

The specific nature of this invention, as well as other objects and advantages thereof, will become apparent to those skilled in the art from the following detailed description of the annexed 3 sheets of drawings which, by way of preferred example only, illustrate one specific embodiment of the invention.

On the drawings;

Figure 1 is a side elevational view of a control linkage for a picker stick of a loom incorporating a rotary type hydraulic check embodying this invention;

Figure 2 is an end elevational view of the assemblage of Figure 1, looking from the rock shaft end of the assemblage; and

Figure 3 is an enlarged scale partial sectional view taken on the plane III-III of Figure 2.

As shown on the drawings:

As is well known, the movements of a picker stick of the loom must be controlled so that the shuttle-engaging portions of a picker, which is conventionally secured to the top end of the picker stick, will travel along a substantially straight line path, generally parallel to the path of the shuttle along the lay of the loom. There have heretofore been proposed a plurality of different types of control linkages for effecting such control of the movements of the picker stick through the pivotal interconnection of a primary bracket which is secured to the rock shaft of the loom and a secondary bracket which is secured to the bottom portion of the picker stick.

A hydraulic checking device embodying this invention may be conveniently incorporated in any type of picker stick control linkage wherein two members of the linkage are pivotally interconnected and are relatively angularly shifted as a function of the movement of the picker stick.

Hence it should be distinctly understood that the I particular control linkage shown on the drawings and to be hereinafter described represents merely a preferred linkage. Referring to the drawings, the linkage shown therein is patterned generally after the control linkage described and claimed in my copending application, Serial No. 37,951 filed July 9, 1948. Such linkage comprises a primary bracket II which is rigidly secured to the rock shaft ID of a loom, and a secondary bracket l2 which is rigidly clamped to the bottom portion of a picker stick I3. Primary bracket H and secondary bracket l2 are pivotally interconnected by a pair of control links M and I and such links are proportioned in such manner as to control the movements of the picker stick [3 so that the shuttle-engaging portion of a picker (not shown) which is conventionally secured to the top end of the picker stick l3, will traverse a substantially horizontal straight line path, generally parallel to the path of the shuttle along the lay of the loom. Links [4 and i5 may obviously constitute either single links or spaced parallel pairs of identical links depending upon the nature of their pivotal supports, and in the particular embodiment shown in the drawings, both the links M and I5 constitute double parallel links.

Primary bracket ll may comprise an integral casting having at one end thereof a split depending portion Ha defining a cylindrical recess to receive the end of rock shaft 10. Split portion Ila is drawn into rigid assemblage with rock shaft In by a clamping bolt 16. Immediately beneath the split portion Ila, the primary bracket ll defines a pivot bearing boss llb to which one end of the link I5 is pivotally secured as by a pivot pin ll." Primary bracket H further comprises an upstanding bifurcated portion He in the ends .of which are defined aligned pivot bearings lld. A pin Ha traverses pivot bearings lid and one end of the control links M, and also provides support for hydraulic check unit 26 in a manner to be described in more detail later.

The secondary bracket l2 may also conveniently comprise a unitary casting having a base portion recessed as indicated at l2a to accommodate the lower portion of the picker stick I3 and be rigidly clamped thereto by a plurality of bolts l9. Secondary bracket [2 further embodies a pair of vertically spaced, lateral projections l2b and l2c, in the ends of which are respectively defined pivot bearings I211 and l2e. The lower pivot bearing 12d pivotally supports the other end of link l5 as by pivot pin llb, while the pivot bearing [2e pivotally journals the other end of link [4 as by pivot pin [10.

The links M and I5 and their pivotal mountings are so proportioned, in the manner described in my above identified copending application, that the movements of the picker stick H will be controlled to produce a substantially horizontal straight line path of movement for the shuttle-engaging portions thereof. In the course of such movement, it is apparent that both the links [G and I5 will have a substantial angular displacement with respect to both the primary bracket H and the secondary bracket l2. Any one of the pivotal connections of the links 14 and IS with either of the brackets H and I2 may be employed to mount a rotary check unit 20 embodying this invention. In the particular example illustrated in the drawings, the pivotal connection between the link I and the primary bracket II has been selected for the mounting of the rotary hydraulic check unit 20.

Referring particularly to Figures 2 and 3 of the drawings, the hydraulic check unit 20 is seen to comprise a cast housing 2| having an open face 21a which is closed by a correspondingly shaped cover 22. Cover 22 is rigidly secured in sealed relationship to housing 2| in any conventional manner.

Housing 2.! is of substantially hollow configuration and its interior is divided by a generally arcuately shaped web portion 2lb which defines on one side thereof a generally sector shaped hydraulic chamber 2E0 and on the other side thereof a reservoir chamber 2111. The arcuate face 2le of the web portion 2lb which defines the hydraulic chamber 210 has a configuration approximating that generated by a radius swung about the axis of the pivotal connection between the link l4 and the primary bracket ll, hence a radius swung about the axis of pivot pin Ha. As best shown in Figure 2, both the end walls of housing 2! and the cover 22 are suitably apertured to permit the pivot pin [hi to pass therethrough and the entire hydraulic unit 20 may thus be disposed intermediate the pair of parallel identical links forming the link M.

A piston 23 is provided having a hub portion 23a, which is mounted upon and keyed to the pivot pin 1 la, by key 2'! and a radially projecting vane portion 231) which cooperates with the walls of the sector shaped hydraulic chamber 2Ic to produce the required fiuid checking action. I

To produce relative movement between the piston vane 23b and the hydraulic chamber 2 lo, the housing 22 is adjustably secured to the primary bracket H, such as by an arm 24 which-has one end thereof welded or otherwise rigidly'secured to the housing 22 and the free end thereof traversed by the threaded portion of an eye bolt 25 which is pivotally secured to the primary bracket II by a pin 25a. Nuts 26 are provided on the eye bolt 25 on each side of the arm 24 and adjustment of the nuts 26 will permit a variation of the secured position of the arm 24 relative to the eye bolt 25 to be effected. This latter variation in turn efiects a minute angular adjustment of the hydraulic unit housing 22 about the pivot pin Hd. Accordingly, the angular relationship of the piston vane 23b and the hydraulic chamber 210 may be conveniently adjusted to vary the angular location of the checking action.

As previously stated, the piston 23 is keyed to the pivot pin Ha for co-rotation. Likewise, the control links I ll are keyed to pivot pin Ila by keys 28. Accordingly, since the housing 22 is fixed to the primary bracket H, and the piston 23 is co-rotatably secured to the links I4, it is apparent that relative angular displacement of the piston vane 23b with respect to the hydraulic chamber 2lc will occur as a function of the angular displacement of the control links [4 with respect to the primary bracket ll, hence as a function of the movement of the picker stick l3.

The contour of the arcuate wall Me of the sector shaped hydraulic chamber 2| 0 is conventionally designed to cooperate with the peripheral end vane 23b to provide the desired double acting checking characteristics. Thus, the central portions Zif of such arcuate wall are recessed outwardly so that substantially no fluid resistance is produced to the movement of the piston vane 23b through the central portions of its angular range of movement. Between the recessed portion Zif and each angular extreme of the chamber Zlc, the arcuate wall 2le is suitably shaped so as to provide a gradually reducing clearance between itself and the cooperating end of piston vane 23b, so that a substantial increase in fluid checking action on the piston vane 23b is produced as the vane approaches either angular end of the hydraulic chamber 2| 0.

To provide temporary accommodation for fluid displaced from the hydraulic chamber 2 lo during the rapid movement of the vane 23b over the nonchecking portions of its range, the casing web 2lb is provided with a plurality of apertures 2Ig which communicate with the reservoir chamber 2ld. In this manner, it is assured that the vane 23b may return relatively rapidly from either extreme end portion of its angular stroke to the central portion without any substantial fluid resistance opposing its movements.

As it well known, it is very desirable that the checking device associated with a picker stick linkage impart substantially no resistance to the power stroke of the picker stick until the picker stick has passed the point on such stroke where the shuttle is thrown. With the construction as described thus far, some resistance to movement of the vane 23b on the initial portions of the power stroke of the picker stick l3 would be encountered by the fact that such vane tends to produce a vacuum behind it when rapidly accelerated from one extreme angular position toward its central position.

To overcome the retarding effects of such vacuum, that end of the hydraulic chamber 2 lo which corresponds to the position of the vane 23b at the beginning of the power stroke of the picker stick is provided with a fluid passage 2|h, which communicates between such end portion of hydraulic chamber 2lc and reservoir chamber 2|d. The fluid passage 21h may be conveniently formed by a hole drilled into the housing 22 and is preferably provided with a reduced diameter portion 2|? at its inner end which provides the actual communication with the reservoir chamber Md. The hole 2 lh communicates radially with the hydraulic chamber 210. A check valve 25 is then slidably mounted in the hole 2 lh and has a conical seating face 25a which cooperates with the shoulder formed at the juncture of small diameter hole 2 I 7' with the larger diameter hole 2lh. Check valve 25 is resiliently urged to its sealing position by a spring 26 which has its other end bottomed on a plug 30 threadably secured in the outer end of the hole 2lh.

With the described construction, the additional passage Zlh between the hydraulic chamber 2| 0 and the reservoir chamber 2|d is effectively closed during the movement of the piston vane 23b toward the end of the hydraulic chamber 2 lo where the fluid passage 2 lh is located. However, upon the return movement of the piston vane 23b, which corresponds to the initiation of the power stroke of the picker stick l3, any excess of pressure developed in the reservoir chamber 2 Id over that existing behind the pistonv vane 23?) I will cause the check valve 25 to open and permit pressure fiow of balancing fluid through the passage 2 l h. In this manner, no vacuum is produced behind the piston vane 23b, and hence substantially no fluid resistance to the movement of the Vane 23b throughout the initial portions of the power stroke of the picker stick I3 is encountered.

During normal operation, the housing 2| is substantially completely filled with a suitable hydraulic fluid. A filling opening 2 im may be provided in that wall of the housing which is the top wall when the checking device is assembled in the picker stick linkage. The filling opening may be closed by a suitable threaded plug 29. I

From the foregoing description, it is apparent that this invention provides a fluid checking device for a picker stick linkage of unusually simple and economically manufacturable construction. The described device will not only provide adequate fluid checking action to both the shuttle throwing and shuttle catching strokes of the picker stick, but in addition, will not produce any substantial fluid resistance to movements of the picker stick during the initial portions of the power stroke. Furthermore, the device is capable of rapid and convenient adjustment of its eiTective checking action through the cooperation of the arm member 24 with the adjusting eye bolt 2'5. Due to its unusual compactness, the described rotary check may be assembled in any picker stick linkage wherein pivotal movement of two parts is involved and will not interfere with the movement of any of the other parts of the picker stick linkage. 7

It will, of course, be understood that various details of construction may be modified through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. In a linkage for controlling the movement of a picker stick of a fly shuttle loom having first and second linkage members pivotally connected and relatively angularly shiftable as a function of the movement of the picker stick, the'improvements comprising a housing defining an hydraulic chamber secured to said first linkage member, a piston vane cooperating with said .hy-

draulic chamber and angularly movablegtherein,

and means connecting said piston vane to said second linkage member, whereby relative pivotal movement of said first and second linkage members produces an angular shifting of said piston in said hydraulic chamber, said hydraulic chamber being constructed and arranged to yieldingly oppose relative angular movement of said piston vane by fluid .checking action, thereby checking the movements of said picker stick.

2. In a linkage for controlling the movement of a picker stick of a fly shuttle loom having first and second linkage members pivotally connected and relatively angularly shiftable as a function of the movement of the picker stick, the improvements comprising a housing secured to said first linkage member and defining a generally sector shaped hydraulic chamber having its axis coincident with the pivotal axis of said linkage members, a piston vane cooperating with said hydraulic chamber and being angularly movable therein about said pivotal axis, and means connecting said piston vane to said second linkage member, whereby relative movements of said linkage members are yieldingly opposed by fluid checking action between said piston and said hydraulic chamber.

3. In a linkage for controlling the movement of a picker stick of a fly shuttle loom having first and second linkage members pivotally connected and relatively angularly shiftable as a function of the movement of the picker stick, the improvements comprising a housing secured to said first linkage member and defining a generally sector shaped hydraulic chamber having its axis coincident with the pivotal axis of said members, a piston vane cooperating with said hydraulic chamber and being angularly movable therein about said pivotal axis, means connecting said piston vane to said second linkage member,

whereby relative movements of said members are yieldingly opposed by fluid checking action between said piston and said hydraulic chamber, said housing also defining a fluid reservoir chamber separate from said hydraulic chamber, and passage gularly central portions of said hydraulic chamher and said reservoir chamber to permit free flow of excess fluid from said hydraulic chamber into said reservoir chamber as said piston vane traverses the central portions of said hydraulic chamber.

4. In a linkage for controlling the movement of a picker stick of a fly shuttle loom having first and second linkage members pivotally connected and relatively angularly shiftable as a function of the movement of the picker stick, the improvements comprising a housing secured to said first linkage member and defining a generally sector shaped hydraulic chamber having its axis coincident with the pivotal axis of said linkage members, a piston vane cooperating with said hydraulic chamber and being angularly movable therein about said pivotal axis, one of the walls of said hydraulic chamber being recessed to permit bypass of fluid around said piston vane through the central portions of the angular movement of said piston in said hydraulic chamber, whereby fluid checking action between said piston vane and said hydraulic chamber occurs only at the end portion of the angular stroke of said piston vane in either direction, and means connecting said piston vane to said second linkage member, whereby the picker stick movement is checked as the picker stick approaches either of its extreme positions.

means communicating between the an- 5. In a linkage for controlling the movement of apicker stick of .a fly shuttle m having first and second linkage members pivotally connected and relatively angularly shiftable as a function of the movement of the picker stick, the improvements comprising a housing secured to said first linkage member and defining a generally sector shaped hydraulic chamber having its axis coincident with the pivotal axis of said linkage members, a piston vane cooperating with said hydraulic chamber and being angularly movable therein about said pivotal axis, the arcuate wall of said sector shaped hydraulic chamber being recessed in the angularly central portions thereof to permit free bypass of fluid around said piston vane, whereby fluid checking action between said piston vane and said hydraulic chamber occurs only at the end portion of the angular stroke of said piston vane in either direction, and means connecting said piston vane to said second linkage member, whereby the picker stick movement is checked as the picker stick approaches either of its extreme positions.

6. In a linkage for controlling the movement of a picker stick of a fly shuttle loom having first and second linkage members pivotally connected and relatively angularly shiitable as a function of the movement of the picker stick, the improvements comprising a housing secured to said first linkage member and defining a generally sector shaped hydraulic chamber having its axis coincident with the pivotal axis of said linkage members, a piston vane cooperating with said hydraulic chamber and being angularly movable therein about said pivotal axis, means connecting said piston vane to said second linkage member, whereby the movements of the picker stick in both its shuttle throwing and shuttle catching directions are checked, means defining a bypass fluid passage between the angular central portions of said hydraulic chamber and the one angular end thereof which effects the. checking of the shuttle catching stroke of the picker stick, and a check valve in said by pass fluid passage permitting fluid flow therethrough only in the direction from said central portions of said hydraulic chamber to said one end portion of said hydraulic chamber, whereby the initial movement of said picker stick on its shuttle throwing stroke is substantially unimpeded by fluid checking action.

7. In a linkage for controlling the movement of a picker stick of a fly shuttle loom having first and second linkage members pivotally connected and relatively angularly shiftable as a function of the movement of the picker stick, the improvements comprising a housing secured to said first linkage member and defining a generally sector-shaped hydraulic chamber having its axis coincident with the pivotal axis of said members, a piston vane cooperating with said hydraulic chamber and being angularly movable therein about said pivotal axis, means connecting said piston vane to said second linkage member, said housing also defining a fluid reservoir chamber separate from said hydraulic chamber, passage means communicating between the angularly central portions of said hydraulic chamber and said reservoir chamber to permit free flow of excess fluid from said hydraulic chamber into said reservoir chamber as said piston vane traverses the central portions of said hydraulic chamber, whereby the movements of the picker stick are checked at the ends of both the shuttle catching and shuttle throwing strokes, means defining a bypass fluid passage between said reservoir chamber and the one angular end of said sector shaped hydraulic chamber Which' effects the checking of the shuttle catching stroke of the picker stick, and a check valve in said bypass fluid passage permitting fluid flow only in the .direction from said reservoir chamber into said hydraulic chamber, whereby the initial movement of the picker stick on its shuttle throwing stroke is substantially unimpeded by fluid checking action.

8. A picker stickcontrol linkage for fly shuttle looms comprising a primary bracket adapted to besecured to the rock shaft of the loom, a secondarybracket adapted to be secured to the picker stick,'a link pivotally connected between said primary and secondary brackets, a housing, means connecting said housing to one of said brackets, said housing defining a generally sector shaped hydraulic chamber having its axis coincident with the axis of the pivotal connection between said link and said one bracket, a piston vane cooperating with said hydraulic chamber and being angularly movable therein about said pivotal axis, and means connecting said piston vane to said link, whereby relative pivotal movement of said link and said one bracket are hydraulically checked.

9. A picker stick control linkage for fly shuttle looms comprising a primary bracket adapted to'be secured to the rock shaft of the loom, a secondary bracket adapted to be secured to the picker stick, a link pivotally connected between said primary and secondary brackets, a housing secured to one of said brackets, said housing defining a generally sector shaped hydraulic chamber having its axis coincident with the axis of the pivotal connection between said link and said one bracket, a piston vane cooperating with said hydraulic chamber and being angularly movable therein about said pivotal axis, and means connecting said piston vane to said link, whereby the movements of the picker stick in both the shuttle throwing and shuttle catching directions are checked, means defining a bypass fluid passage between the angularly central portions of said hydraulic chamber and the one angular end thereof which eifects the checking of the shuttle catching stroke of the picker stick, and a check valve disposed in said bypass fluid passage permitting fluid flow therethrough only in the direction from said central portion to said one end portion of said hydraulic chamber, whereby the initial movement of said picker stick on its shuttle throwing stroke is substantially unimpeded by fluid checking action.

10. A picker stick control linkage for fly shuttle looms comprising a primary bracket adapted to be secured to the rock shaft of the loom, a secondary bracket adapted to be secured to the picker stick, a link pivotally connected between said primary and secondary brackets, a housing secured to one of said brackets, said housing defining a generally sector shaped hydraulic chamber having its axis coincident with the axis of the pivotal connection between said link and said one bracket, a piston vane cooperating with said hydraulic chamber and being angularly movable therein about said pivotal axis, and means connecting said piston vane to said link, said housing also defining a fluid reservoir chamber separate from said hydraulic chamber, passage means communicating between the angularly central portions of said hydraulic chamber and said reservoir chamber to permit free flow of excess fluid from said hydraulic chamber into said reservoir chamber as said piston vane traverses the central portions of said hydraulic chamber, whereby the movements of the picker stick are checked at the ends of both the shuttle catching and a check valve disposed'in said bypass fluid passage permitting fluid flow only in the direction from said reservoir chamber toward said hy-' draulic chamber, whereby the initial movement of said lpicker stickonits shuttle throwing stroke is substantially unimpeded by fluid checking action.

' 11. The combination defined in claim 7 wherein said means connecting said housing to said one bracket includes means for adjusting said housing angularly with respect to said bracket about the axis of connection of said link to said one bracket.

12. A checking device for a parallel motion picker stick linkage of a loom to restrict freedom of motion of relatively movable linkage elements at or near extremities of travel or at any portion of travel comprising, an angularly displaceable vane constructed to be attachable in driven connection with a relatively movable link of said picker stick linkage and a body attachable to a second linkage element defining a hydraulic chamber for said vane, said body having a wall portion defining an arcuate profile of varying cross-sectional contour cooperable with the end portion of said vane to produce accurate checking action by displacement of a checking medium past the end of said vane, said body further defining an adjustable connection to efiect said attachment to said second linkage element, whereby the angular relationship of the arcuate lprofile to said vane may be selectively varied by tilting said body.

13. A checking device for a parallel motion picker stick linkage of a loom to restrict freedom of motion of relatively movable linkage elements at or near extremities of travel or at any portion of travel comprising, an angularly displaceable vane constructed to be attachable in driven connection with a relatively movable link of said picker stick linkage, a compartmented body attachable to a second linkage element and defining a hydraulic chamber for said vane as well as a reservoir adjacent thereto, said body having a compartmenting wall portion defining an arcuate profile of varying cross-sectional contour cooperable with the end portion of said vane, whereby checking action may be produced by displacement of a checking medium past the end of said vane, said wall portion being apertured to place said hydraulic chamber in communication with said reservoir chamber, and a check valve between one end of said hydraulic chamber and said reservoir chamber to permit pressure flow of balancing fluid behind said valve throughout the initial portions of a picker stick power stroke, said body further defining an adjustable connection to effect said attachment to said second linkage element, whereby the angular relationship of the arcuate profile to said vane may be selectively varied by tilting said body.

14. A checking device for a parallel motion lpicker stick linkage on a shuttle loom comprising a body, a web in said body defining an arcuate profile to divide said body into a hy- 11 draulic chamber and a reservoir chamber, a vane angularly movable in said hydraulic chamber with the end portions thereof cooperable with said profile, the .profile of said web being of such a contour as to define a recessed center with gradually reducing clearance portions adjacent thereto, Whereby'the freedomof motion of said vane will be restricted at and near the extremities of movement thereof by the checking action of a checking mediumpast the end of said vane, said vane having, means formed thereon to effect a driven connection with a first relatively movable linkage element of said linkage, and adjustable connection means carried by said body for attachment to a; second, linkage element of said linkage to vary the angular relationship of said profile to said vane for efiecting adjustment of the checking characteristics of; said checking device.

GEORGE I-L I-IUFFERD.

portion 5 12 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

